Conventionally, as this type of drying apparatus, apparatuses for drying a wide variety of materials to be dried, such as granular, powdered, liquid, and massive materials to be dried. Particularly, the present applicant has already proposed drying apparatuses which can implement ideal drying conditions on the basis of a unique blade called Cyclofin (for example, refer to Patent Documents 1 and 2).
In other words, with such drying apparatuses, a material to be dried which has been charged into a vertical cylindrical drying vessel is raised by revolution of a plurality of circular-arc vane sections constituting a rotating vane assembly mounted to a rotating axle, being pressed against a heat-transmitting face of the inner wall of the drying vessel in a thin film state by the centrifugal force, and in addition to this, with an action exerted by a subsequently raised material to be dried to push up a previously raised material to be dried upward, thereby the material to be dried being efficiently dried.
These drying apparatuses have been proposed to solve the problems faced by a drying apparatus having a vertical spiral rotation blade that had been proposed by the present applicant before these drying apparatuses (for example, refer to Patent Document 3), in other words, those of how to prevent a highly viscous material to be dried from adhering to and residing on the blade and the heat-transmitting face; how to prevent a solid substance from being bitten into the clearance between the circular-arc vane section and the heat-transmitting face; how to improve the efficiency of raising the material to be dried; how to effectively utilize the entire face of the heat-transmitting face for improving the drying efficiency; and the like.
Further, the rotating vane assembly is not limited to a single-stage one, and there has been disclosed a multi-stage rotating vane assembly which is configured so as to be arranged in a plurality of stages in a vertical direction. By thus configuring the rotating vane assembly to form a plurality of stages, the material to be dried is raised in sequence by the circular-arc vane section at each stage, while being pressed against the heat-transmitting face to be dried, and then being raised by the circular-arc vane section at the highest stage, thereby a material which has been dried being obtained. In other words, the multi-stage rotating vane assembly has been designed such that the material to be dried is continuously raised while being dried from a bottom portion to an upper portion of the drying vessel.